Friction clutch



Patented Feb. 22, 1938 r} 2 109 435 UNITED STATES PATENT OFFICE Karl Johan Wersiill, Alsten, Sweden Application August 4, 1937, Serial No. 157,428

In Sweden December 31, 1934 2 Claims. (01. 192-105) The invention relates to centrifugal friction drives its own clutch shoe 9, which is free to clutches of the kind in which the shoes are latermove outwards under the action of centrifugal ally turnable and are driven by studs engaging force until arrested by the friction track In. with recesses within them. Each shoe can also rock or turn laterally about One object of the invention is to ensure that its pin. The friction track In is formed asa race the degree or intensity of pressure between the inside apulley H, the boss I2 of which-is rotatably friction surfaces shall be maintained substanmounted on a bush !3 on the sleeve, the boss tially equal over the whole area of a shoe. In and bush being retained in place by the rings l4. clutches as hitherto known, the driving and fric- In order that the clutch shoes shall be enclosed, 10 tional forces acting on each shoe have set up a the drum 5 of the driver is provided with flanges turning moment tending to press the leading 15.

edge of the shoe against the friction drum 01' Each shoe 9 is of a segmental form having two track, with the result that the pressure at the bearing strips 16 which make Contact with the leading part of the shoe has been considerably track or race i0. The recess within which a higher than that at the trailing part. A further driving stud engages is in the form of a slot I1 15- object of the invention is therefore to provide having a contact surface It at each end. a shoe which is suitable for a clutch which is to Referring to Figure 2, as the shoe 9 is symdrive in both directions and which ensures a metrical about its radial centre line 19, the substantially even distribution of pressure over point of action of the frictional forces acting on 20 the whole friction surface of the shoe, irrespective the shoe lies on the centre line and is located 20 of the direction in which it is rotating. at the point 20 just outside the surface of the According to the present invention, the contact track I0, this point 20 coinciding with the intersurface of the recess, in the shoe, with which the section of tangents to the shoe periphery, repredriving stud engages is so inclined to the radial senting the resultants of forces on each side of centre line of the shoe that a line perpendicular the radial center line 19. A normal 2| to the con- 25 to, and passing through the centre of, said surtact surface l8, drawn at the centre point 22 of face passes through, or near, the point of action the surface, passes through the point of action 20. of the frictional forces acting on the shoe. Fur- In this arrangement, the line of the driving ther, according to the invention, the driving stud force exerted on the shoe by the stud passes acts near the leading end of its respective shoe so through the point of action of the frictional forces, 30 that the greater part of the shoe is trailing, and, and the greater part of the shoe trails behind in order that the shoe may be employed for the driving stud. The tendency for the leading driving in either direction, the recess within which edge of the shoe to rock outwardly about the stud the stud engages is in the form of a slot or groove is reduced, so that the degree of pressure is subextending almost from end to end of the shoe. stantially the same over the whole area of the 35 Each end of the slot may be provided with the bearing strips I6. The uniform distribution of special contact surface for the stud as above pressure over the whole area of a shoe effects mentioned. a substantial increase in the life of the shoes One form of the invention is illustrated by Way and of the friction track. of example in the accomp y drawing, in The provision of the long slot I! with a prop- 40 Whichlerly formed contact surface l8 at each end per- Figure 1 is a side sectional elevation through mits the advantages of the invention to be halt: of a ceetrlfugal clutch tained in a reversible clutch, irrespective of the Figure 2 being a somewhat diagrammatm crossdirection of the drive a sectional elevation of a portion of the clutch cor- In the case of a unidirectional clutch th 45 responding thereto.

slot ll need only be long enough to enable the Flgme 3 1s a plan of Shoe shoe to move with perfect freedom on its stud.

Referring to the drawing, a sleeve I having its centre line at 2, can be secured to a driving In thls case consldenng clutch dnvmg m an shaft. A driver 4 is keyed to the sleeve and is anti-clockwise diliection as in Figure the point 50 in the f of a drum 5 provided with a central of action would he to the right of the geometric rib or web a in which driving studs 1 are centre line of the shoe owing to the difference in cured, Th driving t d r equally Spaced the position of the centre of gravity of the more around the driver and have contact heads 8 in solid shoe.

the form of frustra of inverted cones. Each stud In practice, it is found that the normal 2| may 55 deviate up to 15 on either side of the point 20 Without serious loss of efliciency of the clutch.

The mere driving of the shoes near their leading edges in itself does much to distribute evenly the pressure over the whole area of the shoes. The provision of a slot extending over a substantial length of the shoe is of great utility in a reversible clutch as, irrespective of the direction of rotation, the shoes can be driven near their leading edges with a substantial portion of the shoes trailing. A more or less uniform distribution of pressure is thus obtained in both directions of rotation. V 1 I When driving studs having cylindrical instead of conical heads are employed, the studs are inserted angularly or tangentially, that is, not radially, into the driver in order that the contact surfaces of the shoes shall be correctly inclined for the purpose of the invention.

I claim:

1. A centrifugal clutch comprising a friction track, a driving member, studs carried by said driving member, shoes adapted to be driven by said studs and to engage frictionally with said track under centrifugal action, each of said shoes friction track.

2. A centrifugal clutch comprising a friction track, a drivingmember, studs carried by said driving member, shoes adapted to be driven by said studs and to engage frictionally with said track under centrifugal action, each of said shoes having an elongated slot extending substantially from end to end of the shoe and a contact surface at each end of said slot for alternative driving engagement by the stud received in said slot, to render the clutch reversible, each of said contact surfaces being so inclined to the radial center line of said shoe that a line perpendicular to and passing through the center of said surface intersects said radial center line at a point adjacent to but beyond said frictional track.

KARL JOHAN WERsALL" 

